JP3303606B2 - Method of forming multilayer thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming a multilayer thin film by a plasma CVD method in a plurality of vacuum reaction chambers for manufacturing a thin film solar cell or the like.

[0002]

2. Description of the Related Art Conventionally, in forming a multilayer thin film, a conductive susceptor (holding body) on which a substrate is mounted is used as one electrode, and a high voltage is applied to a high-voltage electrode opposed to the electrode to form a multilayer in a vacuum reaction chamber. Discharge occurred, and a thin film was deposited on the substrate by plasma CVD or sputtering. FIG. 2 shows a conventional film forming apparatus for manufacturing an amorphous silicon (a-Si) solar cell, in which a multilayer thin film is formed in four vacuum reaction chambers 12 to 15 sandwiched between a loading chamber 11 and a loading chamber 16. I do. The reaction chamber 12 is a chamber for forming a p-type amorphous silicon oxide or a p-type amorphous silicon carbide on a glass substrate 1 on which a transparent electrode is formed by plasma CVD. The reaction chamber 13 is made i
This is a chamber for depositing quality a-Si. The reaction chamber 14 is a chamber for forming an n-type a-Si film by plasma CVD. The reaction chamber 15 is a chamber for forming a metal electrode by sputtering.
The glass substrate 1 is mounted on a conductive susceptor 2 made of stainless steel or the like via an insulating material 21, a gate valve 17 is opened, and the glass substrate 1 is placed on a substrate table 18 of a loading chamber 11. Then, the gate valve 17 between the chambers is opened and closed to sequentially move the susceptor 2 together with the susceptor 2 onto the support 3 heated by the heater 31 in each of the reaction chambers 12 to 15. Plasma CV
In the D chambers 12, 13, and 14, a voltage is applied to the high-voltage electrode 5 connected to the high-frequency electrode 4 to generate plasma in a different reaction gas depending on the chamber. In the sputtering chamber 15, a high voltage is applied to a target 6 such as Ag or Al connected to the high-frequency power supply 4 to perform sputtering. The substrate 1 on which the film formation has been completed is moved together with the susceptor to the carry-out chamber 16, and after breaking the vacuum, the gate valve 17 is opened and taken out. Since the vacuum is not broken when the substrate 1 is moved between the reaction chambers 12 to 15, a multilayer thin film having a good interface can be formed.

[0003]

The characteristics of the thin film thus formed are affected by ions incident on the substrate. However, the amount and energy of ions incident on the substrate are determined by the electrode shape and pressure, the type of reaction gas, and the like, and cannot be controlled independently of the discharge state. Therefore,
In a film forming apparatus having only one vacuum reaction chamber, it has been attempted to control the amount and energy of ions incident on the conductive substrate by applying a DC bias voltage of, for example, 100 V to the conductive substrate from the outside through a voltage introducing terminal. Have been. However, in a multilayer thin film forming apparatus in which a conductive substrate moves in a plurality of vacuum reaction chambers as shown in FIG. 2, it is necessary to remove and attach the conductive terminals to and from the substrate every time the vacuum reaction chamber moves. And it was difficult to apply a DC bias voltage to the substrate. After depositing a film of a-Si or the like having a low conductivity of 10 ^-8 to 10 ^-11 S / cm on the substrate, electrical connection is established even when a conductive terminal is brought into contact with the exposed surface of the substrate. There was a problem that could not be done. Furthermore, since the substrate and the susceptor are heated by the heater, there has been a problem that the electrical connection to the substrate becomes unstable.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems, control the amount and energy of ions incident on the substrate by applying a stable DC bias power to the substrate, and stack thin films having desired characteristics. It is an object of the present invention to provide a method for forming a multilayer thin film that can be performed.

[0005]

In order to achieve the above object, a substrate on which a film is to be formed is mounted on a conductive holder and passed through a plurality of vacuum reaction chambers. In a method for forming a multilayer thin film in which a high-frequency voltage is applied between opposing electrodes and a thin film is sequentially deposited on a substrate heated to a predetermined temperature, the first present invention according to claim 1 includes the steps of: Mounted on a holder via an insulator, equipped with a high temperature resistant DC power supply on the holder, and passing the holder through each reaction chamber while applying a predetermined DC bias voltage between the substrate and the holder. And According to a second aspect of the present invention, a plurality of substrates insulated from each other are mounted on a holder via an insulator, a high-temperature resistant DC power supply is provided on the holder, and a predetermined The holder is passed through each reaction chamber while applying a DC bias voltage. In any case, a discharge is generated between the substrate and the counter electrode in the vacuum reaction chamber to generate the plasma CV.
It is effective to deposit a thin film on the substrate by D. It is also preferable to use a storage battery for the high-temperature resistant DC power supply, and particularly to use a solid electrolyte storage battery. A solar cell is preferably used as the high-temperature resistant DC power supply, and an a-Si solar cell is particularly preferably used. It is also preferable to use a thermoelectric generator as the high-temperature resistant DC power supply, and particularly to use a semiconductor as the thermoelectric material.

[0006]

A high-temperature resistant DC power supply is provided on the holder, and the power supply is provided between the holder on which the film-forming substrate is mounted via the insulator and the counter electrode, or on a plurality of substrates mounted insulated from each other on the holder. When a DC bias voltage for controlling ions incident on the substrate is applied between the film forming substrates, the film quality of the thin film formed in each vacuum reaction chamber while passing the holder and the substrate in each vacuum reaction chamber while maintaining the state is maintained. Controlled. It is known that control of film quality by controlling incident ions is effective in film formation by plasma CVD. A storage battery, particularly a solid electrolyte storage battery that can withstand temperatures up to about 130 ° C., is used as the high-temperature resistant DC power supply. Alternatively, a solar cell, particularly an a-Si solar cell using a temperature of about 200 ° C. during manufacturing, a thermoelectric generator, and particularly a semiconductor having a high thermoelectromotive force by using a semiconductor as its thermoelectric material, has a high thermoelectromotive force from 250 ° C. to 1100 Use a thermoelectric generator that can withstand temperatures up to ° C.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings in which parts common to those in FIG. FIG. 1 shows a method for forming a multilayer thin film for manufacturing an a-Si solar cell according to one embodiment of the present invention. Vacuum reaction chambers 12, 13, and 14 for performing plasma CVD between the loading chamber 11 and the unloading chamber 16 as in FIG.
And a vacuum reaction chamber 15 for performing sputtering.
Conductive susceptor 2 on which substrate 1 is mounted via insulating material 21
Moves through the respective chambers 11 to 16 as in FIG. 2, but a DC power supply 7 is installed on the susceptor 2. One terminal of the DC power supply 7 is connected to the susceptor 2 having the same potential as the grounded support 3, and the other terminal is connected to the substrate 1 via the bias port 8.

Then, a bias voltage of, for example, about 5 V, which is previously selected, is applied by the DC power supply 7 so that the amount and energy of ions incident on the substrate are optimized. For example,
When forming an a-Si based semiconductor by plasma CVD, the susceptor 2 is heated by the heater 31 of the support base 3 to raise the substrate temperature to about 200 ° C., so that the DC power supply 7 has high temperature resistance. It costs.

In another embodiment of the present invention shown in FIG. 3, two substrates 41, 5 are interposed via an insulating material 21 on a susceptor 2.
1 is mounted, and a DC bias voltage is applied between the two substrates by the high temperature resistant DC power supply 7. This makes it possible to control the ions incident on each substrate in a state where the substrates 41 and 51 are floated with respect to the high-voltage electrode 5 and the susceptor 2 that generate electric discharge.

FIGS. 4 to 6 show embodiments using various high-temperature resistant DC power supplies. In the embodiment shown in FIG. 4, a storage battery 71 that can withstand high temperatures is used for a high-temperature resistant DC power supply. The high temperature resistant storage battery 71 may be a lithium thionyl chloride battery at a temperature of 85 ° C. or lower, but a solid electric field battery such as a lithium iodide solid electrolyte battery at a higher temperature and a polyethylene oxide or LiFCO ₃ solid electrolyte battery at about 130 ° C. Use a quality storage battery.

In the embodiment shown in FIG. 5, an a-Si solar cell 7 manufactured at a temperature of 200.degree.
2 is used. The back surface of the solar cell 72 is a negative electrode and is in contact with the susceptor 2. As the substrate, a substrate having a transparent electrode 43 provided on a glass plate 42 is used. The transparent electrode 43 is connected to the solar cell 72 by the bias port 8.
Is connected to the positive electrode on the surface. In this case, the glass plate 42
Also serves as an insulator. Substrate 7 using plasma emission as light source
The solar cell generates electric power by the light transmitted through it and works as a high-temperature resistant DC power supply. If the size of the solar cell 72 is the same as or smaller than the substrate 51, the solar cell 72 can be repeatedly used without forming a thin film on the surface of the solar cell 72.

In the embodiment shown in FIG. 6, a thermoelectric generator 73 is used as a high-temperature resistant DC power supply. A thermoelectric generator is a device in which different types of semiconductors or conductors are joined at both ends thereof, and power is generated using a thermoelectric effect when a temperature or the like is applied to a junction. The substrate 1 is made of a thermoelectric material 7 for a positive electrode such as a p-type semiconductor.
The susceptor 5 is connected to a thermoelectric material 75 for a negative electrode such as an n-type semiconductor via a bias port 8.
The junction on the other side of the thermoelectric material 74 for the positive electrode and the thermoelectric material 75 for the negative electrode is heated by contacting the susceptor 2 heated by the heater 3, so that a DC bias voltage is applied between the substrate 1 and the susceptor 2. You. Semiconductors having high thermoelectric power used for the positive electrode electrothermal material 74 or the negative electrode thermoelectric material 75 include Bi ₂ Te ₃ , Bi ₂ (Te.Se) ₃ ,
i, Ge, Te, Bi ₈₈ Sb ₁₂ , Sb ₂ Te ₃ , B
i ₃ , Se ₂ , PbTe, Cu _1.97 Ag _0.03 S
e _1.0045 , GeTe, Ge ₃ Si ₇ , FeSi, α-A
such lB ₁₂ and the like, using these alone or as a mixture. The thermoelectric power for Pt of a substance often used as a material of a conventional thermocouple is −35.0 μm in constantan.
V / K, -12.9 μV / K for Alumel, +7 for Cu.
7 μV / K and +28.1 μV / K for chromel.
On the other hand, the thermoelectric power for Pt of the semiconductor is, for example, −184 μV / K for Bi ₂ (Te · Se) ₃ , n
-166μV / K in the form Bi ₂ Te _3, p-type Bi ₂ Te ₃
+243 μV / K for Ge, 339 μV / K for Ge, +
448 μV / K, one to two orders of magnitude higher than conventional thermocouple materials. And, for example, BiTe-based material is 250 ° C.
PbTe-based material is 600 ° C., GeSi-based material is 1100
° C, and an electromotive force usable as a high-temperature resistant DC power supply can be obtained by connecting a plurality of pairs in series as needed.

[0013]

According to the present invention, a high-temperature DC power supply is provided on a holder for a substrate on which a film is to be formed, so that the substrate can be held together with the holder in a vacuum with the substrate heated without disconnecting the connection for applying a DC bias. It became possible to move between each reaction chamber. This makes it possible to apply a DC bias voltage to the substrate in each chamber of the multilayer thin film deposition apparatus having a plurality of vacuum reaction chambers utilizing discharge, thereby controlling the amount and energy of ions incident on the substrate. Thus, the quality of the thin film can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an a-Si solar cell manufacturing apparatus capable of performing a method for forming a multilayer thin film according to the first invention.

FIG. 2 is a cross-sectional view of a conventional a-Si solar cell manufacturing apparatus.

FIG. 3 is a sectional view of a susceptor used in a method for forming a multilayer thin film according to a second embodiment of the present invention;

FIG. 4 is a sectional view of an example of a susceptor used in the method for forming a multilayer thin film according to the first embodiment of the present invention;

FIG. 5 is a sectional view of another example of the susceptor used in the method for forming a multilayer thin film according to the first embodiment of the present invention;

FIG. 6 is a sectional view of another example of the susceptor used in the method for forming a multilayer thin film according to the first embodiment of the present invention;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 41, 51 Substrate 2 Susceptor 21 Insulating material 3 Support base 31 Heater 4 High frequency power supply 5 High voltage power supply 6 Target 7 High temperature resistant DC power supply 8 Bias port 11 Loading chamber 12, 13, 14 Plasma CVD chamber 15 Sputtering chamber 16 Loading chamber 17 Gate valve 42 Glass plate 43 Transparent electrode 71 High temperature resistant storage battery 72 Solar cell 73 Thermoelectric generator

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-4-65120 (JP, A) JP-A-6-267861 (JP, A) JP-A-60-149119 (JP, A) JP-A-6-149119 41757 (JP, A) JP-A-63-162874 (JP, A) JP-A-62-29841 (JP, A) JP-A-1-103828 (JP, A) JP-A-5-63223 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/205 C23C 16/50 C23C 16/54

Claims (9)

(57) [Claims] 1. A substrate on which a film is to be formed is mounted on a holder, passed through a plurality of vacuum reaction chambers, and a high-frequency voltage is applied between the holder and an opposing electrode in each reaction chamber to reach a predetermined temperature. In a method for forming a multilayer thin film in which thin films are sequentially deposited on a heated substrate, the substrate is mounted on a holder via an insulator, a high-temperature DC power supply is provided on the holder, and the substrate and the holder are connected to each other. A method for forming a multilayer thin film, wherein a holder is passed through each reaction chamber while a predetermined DC bias voltage is applied therebetween. 2. A substrate on which a film is to be formed is mounted on a holder, passed through a plurality of vacuum reaction chambers, and a high-frequency voltage is applied between the holder and an opposing electrode in each reaction chamber to reach a predetermined temperature. In a multilayer thin film deposition method of sequentially depositing a thin film on a heated substrate, a plurality of substrates that are insulated from each other are mounted on a holder via an insulator, and a high-temperature resistant DC power supply is provided on the holder, A method for forming a multilayer thin film, comprising: passing a holder through each reaction chamber while applying a predetermined DC bias voltage between substrates. 3. The method according to claim 1, wherein a discharge is generated between the substrate and the counter electrode in the vacuum reaction chamber to deposit the thin film on the substrate by plasma CVD. 4. A storage battery is used as a high-temperature resistant DC power supply.
4. The method for forming a multilayer thin film according to any one of items 3 to 3. 5. The method for forming a multilayer thin film according to claim 4, wherein a solid electrolyte storage battery is used. 6. The method for forming a multilayer thin film according to claim 1, wherein a solar cell is used as a high temperature resistant DC power supply. 7. The method according to claim 6, wherein an amorphous silicon solar cell is used. 8. The method for forming a multilayer thin film according to claim 1, wherein a thermoelectric generator is used as a high-temperature resistant DC power supply. 9. The method according to claim 8, wherein a semiconductor is used as a thermoelectric material of the thermoelectric generator.